Calendar: 1866-1867 Page 476

478 APPLIED SCIENCES If the distance of the mirror from the lens must be Shew that an astronomical telescope furnished with Rams- den's eye-piece the focal length of the object-glass of which is 75 times that of either lens of the eye-piece magnifies 100 times 10 Describe Newton's telescope and trace the path of pencil through it from distant point not in the axis the eye- piece consisting of single lens 11 What is the dispersion of light Explain the coloured outline given to the images of objects viewed through prism or single lens How is it possible to get an achromatic image of any object by placing lenses close together Explain how it is that achromatism is possible when the lenses are arranged as in Huyghen's eye-piece 12 Two equal and similar concavo-convex lenses of crown- glass -J of small thickness the radii of the convex sur- faces being inches and of the concave surfaces fths of an inch are placed so as to contain water between them Find the principal focus of the combination SECOND YEAR Find the position of the centre of gravity of truncated cone of which the radii of the ends are and 10 inches and height inches If it be placed on its small end on horizontal plane find the work expended in pushing it over wheel and axle is just on the point of moving about rough axis find the mechanical advantage gained when weight is raised by means of it Find the mechanical advantage when the radii are and 18 inches the radius of the axis inches and the limiting angle of friction 8in י